Inspecting integrated circuits (ICs) for defects is an essential part of the IC manufacturing process. Inspection typically includes electrically testing individual IC dies on a wafer to determine if a selected IC die is functional or not. A probe card having multiple probes is coupled to a manipulator, and the wafers to be tested are loaded onto a wafer handler. To test for proper electrical connectivity, the IC tester might send electrical test signals via the probe card to the selected IC die, and the probe card sends a response signal from the IC back to the IC tester. The IC tester evaluates whether or not the test response signal is within an acceptable range. If the test response signal is acceptable, then additional dies on the wafer may be tested, until the wafer has passed the inspection, and then the manufacturing process in continued. If the test response signal is not acceptable, then the wafer is failed.
Before such testing can occur, however, the probe card and wafer are manually aligned with each other such that the probe's tips can touch down onto the bond pads of the selected IC die. Typically, the IC tester records the lateral position of the probe tips relative to the wafer, so that subsequent identical wafers to be tested can be identically positioned.
Traditional methods and instruments to perform such electrical testing are done at room temperature or at a single elevated temperature. When wafers are to be tested at an elevated temperature, to avoid misalignment between the probe tips and the pads, it is sometimes necessary to repeat the manual alignment process and re-record the position of the probe card. Repeating the manual alignment is time consuming because the testing equipment is designed to require the operator to remove the wafer from the wafer handler, adjust the temperature of the handler, and then return the wafer to the handler, before doing the manual alignment process.